Imagine a Melbourne homeowner who has spent months planning a compact 60 m² granny flat for an ageing parent. The two-bedroom layout works, but the living room is tight and there is no separate space for visiting family. Then the homeowner hears that Victoria's planning definition now allows a small second dwelling of up to 80 m².
The immediate question is understandable: should the plan become larger?
An extra 20 m² can improve room sizes, storage and flexibility. It can also spread the building further across the backyard, increase the construction scope and leave less useful outdoor space. The new maximum creates a choice, not a reason to automatically build to the limit.
What changed in Victoria?
Planning Victoria states that Amendment VC306 took effect on 15 October 2026 and increased the maximum floor area in the planning definition of a small second dwelling from 60 m² to 80 m².
Under the current planning definition, the floor area:
- includes all floors used as the self-contained residence
- is measured from the outside surface of external walls, or the centre of a relevant party wall
- excludes specified attached or abutting outdoor structures, including unroofed patios and roofed decks or verandahs
This is a planning change. Planning Victoria also says the corresponding changes are proposed to be reflected in the building system, including the Building Regulations 2018 and Minister's Guideline 12. A building permit is normally required for a small second dwelling.
That transition matters. Before relying on a design above 60 m², confirm the current pathway with the relevant building surveyor, designer and council. The broader Victoria granny flat rules guide explains why the property still needs a site-specific check.
The short answer: choose the area after choosing the job
An 80 m² granny flat is not automatically more liveable than a good 60 m² design. Floor area only helps when it is allocated to something the occupants will use.
Start by defining the job of the home:
- long-term accommodation for one person or a couple
- a two-bedroom home for family members
- a larger home for several occupants
- flexible space for care, study or regular guests
- a rental considered alongside local demand and operating costs
Then test the smallest layout that supports those needs comfortably. This keeps the design focused and makes the budget comparison more meaningful.
60 m² versus 80 m² at a glance
| Decision factor | Around 60 m² | Up to 80 m² |
|---|---|---|
| Typical strength | Compact two-bedroom living or a generous one-bedroom home | More room for a third bedroom, larger shared spaces or added amenities |
| Backyard impact | Generally preserves more open area | Spreads further across the property unless the footprint becomes more efficient |
| Circulation | Encourages a compact room sequence | Can improve separation, but may also add hallways |
| Storage | Needs careful integration | More opportunity for linen, robes or a pantry |
| Wet areas | Usually rewards a simple grouped layout | May support a second bathroom or separate laundry if genuinely needed |
| Construction scope | Smaller building envelope | More foundation, structure, external envelope and finishes in many designs |
| Site sensitivity | Still depends on access, services and constraints | Requires even closer testing of the remaining yard and site requirements |
The comparison is conceptual. Bedroom count, internal usable area and final project cost depend on the actual plan, specification and block.
What can the extra 20 m² improve?
Better rooms rather than more rooms
The strongest use of extra area may be a more comfortable living room, better furniture clearances, wider circulation or practical storage. These improvements are less visible on a marketing plan than an extra bedroom, but they can matter more in daily life.
Homeowners should compare the proposed room arrangement with the broader options on the granny flat designs page, rather than judging the design by its total area alone.
A third bedroom
Moving towards 80 m² can make a three-bedroom layout less compressed. It may provide better robe space, room proportions or separation between bedrooms and living areas.
A third bedroom should still have a clear purpose. If it forces the kitchen and living area into a leftover zone, the larger plan may carry more rooms without becoming a better home. Compare the intended occupants with the choices on the three-bedroom granny flats page.
A second bathroom or separate laundry
For several adults, an additional toilet, ensuite or separate laundry can improve daily routines. These choices also add fixtures, waterproofing, plumbing and ventilation scope.
The question is not whether the room fits on the drawing. It is whether the expected use justifies the area and project scope it consumes.
A study or flexible room
A work area can be useful without becoming another fully enclosed room. A study nook, wider living zone or adaptable bedroom may deliver more flexibility with less circulation.
For a smaller household, a well-planned two-bedroom granny flat may still be stronger than an 80 m² plan filled with rooms that are rarely used.
When is the compact option likely to be stronger?
A design closer to 60 m² may be the better decision when:
- one person or a couple will be the main occupants
- two bedrooms and one bathroom support the real household need
- preserving lawn, garden or private outdoor space is important
- access and service routes already make the site challenging
- the extra area would mostly become hallway or oversized rooms
- the budget is better directed towards site works, comfort, storage or durable finishes
Compact does not have to mean cramped. Clear furniture plans, good window placement and short circulation can make a smaller home work efficiently.
When may an 80 m² design make sense?
A larger design may be justified when:
- three genuine bedrooms are needed
- several adults will share the home long term
- accessibility and care needs require more circulation or bathroom space
- the block can retain useful open space after the larger footprint is placed
- the additional project scope has been included in a realistic budget
- the design has been checked against the current planning and building requirements
The key is that every additional area has a job. If the plan cannot explain where the extra 20 m² goes, larger may simply mean more building to fund, maintain and fit on the site.
Test the whole block before increasing the floor area
The building limit is not the same as the buildable area on a particular property. A larger footprint can affect:
- setbacks and relationships with boundaries
- site coverage and permeable area
- garden area where relevant
- private open space for both dwellings
- daylight, overlooking and overshadowing
- retained trees and landscaping
- easements, drainage and service routes
- pedestrian and construction access
A roofed outdoor area may be excluded from the current small-second-dwelling floor-area definition, but that does not mean it disappears from every other site calculation. Planning Victoria's garden-area guidance, for example, treats buildings and roofed outdoor areas differently from open garden space.
Draw the main house, the proposed dwelling, paths, services, outdoor areas and retained landscape on the same site plan. That reveals whether the larger design improves the property or simply fills more of it.
How does a larger plan affect the budget?
There is no reliable universal price difference between a 60 m² and 80 m² granny flat. The additional cost depends on the design, site, construction system, specification and services.
In many proposals, extra floor area can change quantities for:
- foundations and floor structure
- framing, roof and cladding
- insulation, plaster, painting and flooring
- windows and external doors
- electrical, heating and cooling coverage
- cabinetry, robes and internal doors
- drainage and external works around the wider footprint
Some project costs do not increase in a straight line with floor area. Design, permits, reports, service upgrades, access work and site-specific foundations can make two similar-sized projects very different.
Use the granny flat cost guide for Victoria to separate the building scope from the complete project budget. When comparing sizes, request both options with the same inclusions, site assumptions and external works.
A five-step size decision
1. Write the occupant brief
List who will live there, how long they may stay, furniture needs, privacy expectations, accessibility needs and the rooms used every day.
2. Test furniture before adding rooms
Place beds, sofas, dining furniture, appliances, robes and door swings on the plan. A slightly larger room may solve more than another enclosed space.
3. Compare internal usable area
Because the planning floor area is measured to the outside of external walls, do not assume an 80 m² limit provides 80 m² of internal room area. Ask for a clear area schedule.
4. Place both options on the site plan
Compare what remains outside the building, not just what appears inside it. Check access, outdoor use, landscaping, services and privacy for both dwellings.
5. Obtain same-scope advice and pricing
Ask the designer or builder to identify what changes between the two options. Confirm current permit requirements, building-system treatment and the items included in each quote before choosing.
Questions to ask before approving an 80 m² concept
- What is the measured planning floor area and how was it calculated?
- What is the estimated internal usable area?
- Which room or function uses each part of the additional area?
- How much private open space and permeable area remains?
- Are decks, verandahs and paths shown consistently on the site plan and quote?
- Has the current building pathway for a design above 60 m² been confirmed?
- Are both size options priced using the same specification and site assumptions?
These questions turn a maximum area into a practical design decision.
Start with the property, not the new limit
If you are deciding whether a 60 m² or 80 m² granny flat suits your property, MPLUS can review the address, available backyard area, access and obvious land constraints before you commit to the larger option. Submit the property details through the Free Land Check for an initial site-fit review.
